Re: Pole Position monitor blowing fuse

From: Christopher X. Candreva <>
Date: Sat Apr 17 2010 - 21:03:23 EDT

On Sat, 17 Apr 2010, John Robertson wrote:

> Well, the first thing to check is if the horizontal output transistor (HOT) is
> shorted. You need to remove it or unsolder the emitter and base leads to check
> that out. If it is shorted then you need to check if the flyback is good or
> bad - I happen to sell an in-circuit flyback tester that can help here
> ($42US), and it is good for testing flybacks in both raster and vector
> monitors...(sorry about the ad) or you can borrow one of these from someone on
> this list - we have sold a few to regulars here

:-) No prob on the ad -- I may have one actually, I know I bought some kind
of flyback tester some years ago.

> I find that the flyback or HOT fail from capacitors breaking down - a good
> argument for checking caps every now and then for signs of heating up (plastic
> film on cap appears to shrink back from covering 1/3 of the top of the cap) or
> monitor changing size, etc. are clues that it is time for recapping. Many
> recap kits are using inexpensive capacitors that do not meet factory standards

The caps look good, I did inspect them to see if any had blown their
top. They all look as clean as when I put them in. This was a Bob Roberts
cap kit, installed 5 years ago, and in my basement has probably had no more
then 200 running hours, probably closer to 100. The flyback was replaced
with one from Bob at the same time. Checking my mail, the flyback was
shooting flame at the time, and I did the cap kit while I had it out.

> Of course the blown fuse could be simply a shorted diode on the primary B+
> supply...

Will check that too.

And Matt -- thanks for your suggestion. It's blowing instantly, but not
turning into molten slag. It's I think a 1.5 amp fuse, fairly thin, if I
recall the original fuse had just an empty tube when I looked at it, the one
I put in just has the filament broken.

Chris Candreva -- -- (914) 948-3162
WestNet Internet Services of Westchester
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Received on Sat Apr 17 21:03:24 2010

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